[Tests] Remove filesystem mocks in copy-by-pattern.test.ts

[gonzaloriestra]

WHY are these changes introduced?

Mocks for the filesystem can lead to tests that pass but don't actually verify the real behavior of the code on disk. This is especially true for services that use fileRealPath or other operations that depend on path existence.

WHAT is this pull request doing?

Refactors packages/app/src/cli/services/build/steps/include-assets/copy-by-pattern.test.ts to remove global vi.mock('@shopify/cli-kit/node/fs'). It now uses inTemporaryDirectory and real filesystem operations (mkdir, writeFile, fileExists) to verify the behavior of the copyByPattern service.

How to test your changes?

CI

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

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PR created automatically by Jules for task 5074333505735786815 started by @gonzaloriestra

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